“I’m not Finn Hudson,” actor Cory Monteith says of his beloved Glee character in an exclusive interview in this Sunday’s PARADE with Shawna Malcom. Opening up about his troubled past as he never has before, Monteith explains, “I’m lucky on so many counts—I’m lucky to be alive.”

The actor grew up in Victoria, British Columbia, feeling like an outsider. His parents divorced when he was 7, and by 13, Monteith—once a promising student who at age 5 could read at a fourth-grade level—was skipping school to get drunk and smoke pot. Monteith estimates that by the age of 16, when he quit for good, he had attended 12 different schools, including alternative programs for troubled teens. “I burned a lot of bridges,” he says. “I was out of control.”

At that point, so was his drug use. Monteith admits, “Anything and everything, as much as possible,” he says. “I had a serious problem.”

Afraid that he “could die,” his mother and a group of friends staged an intervention when he was 19. “That’s when I first went to rehab. I did the stint but then went back to doing exactly what I left off doing.” Monteith might have continued down that path if not for what he calls “the crystallizing event.”

“I stole a significant amount of money from a family member,” he admits. “I knew I was going to get caught, but I was so desperate I didn’t care. It was a cry for help. I was confronted and I said, ‘Yeah, it was me.’ It was the first honorable, truthful thing that had come out of my mouth in years.”

He was given an ultimatum: Get clean, or the family member would report him to the police and press charges. Although it wasn’t the first time Monteith had taken something that didn’t belong to him (“A lot of things went missing when I was around; I had high overhead to take care of ”), up until that point he had avoided prosecution.

Monteith moved in with a family friend in the small Canadian city of Nanaimo, where he quit using drugs, got a job as a roofer and began the process of rebuilding his life. He worked with an acting coach who put Monteith in front of the camera to do a scene about a guy contemplating suicide. It was a life-altering moment for Monteith, the first time he’d felt the satisfaction of “working hard and being good at something.”

The perspective Monteith has gained is part of the reason he is choosing to speak out about his past now. He tells PARADE, “I don’t want kids to think it’s okay to drop out of school and get high, and they’ll be famous actors, too. … But for those people who might give up: Get real about what you want and go after it. If I can, anyone can.”

Along with career success have come personal victories. This spring, Monteith received a high school diploma from an alternative school he attended in Victoria, British Columbia. And in late 2009, he reunited with his father for the first time in 17 years. “We’d spoken maybe three or four times [during that period],” Monteith says, “and he reached out to me on Facebook. I couldn’t shut the door, so I got on a plane. He greeted me at the airport, and [he and Monteith’s stepmother] were so happy they were almost crying. It was a good time. At some point, you realize your parents are human. They make the best decisions they can with the options available to them.”

Be sure to check out this weekend’s issue of PARADE magazine for the full interview with Cory Monteith.